1. Field of the Invention
The invention relates generally to pistons, and more particularly to a piston having a combustion bowl and a method of making a piston with a combustion bowl.
2. Related Art
Many one-piece pistons for internal combustion engines have a crown and a skirt which are forged or cast to a near-final form as one integral piece. The piston is then typically machined through a conventional turning process to remove excess material formed during the forging or casting process and to give the one-piece piston its final form. A combustion bowl, which may be preferred for pistons for diesel fueled engines, may also be machined into the top surface of the crown during the turning process.
Other one-piece pistons are initially cast or forged as two separate pieces which are subsequently joined together. This may be advantageous over pistons of one integral piece as it may allow for complex features, such as oil galleries, to be formed into the piston which would otherwise be impossible, or at least commercially impractical, through conventional casting or forging processes. Once the two pieces are joined together, the one-piece piston is mounted on a conventional machine tool, such as a lathe, which machines certain features into the piston. Features which are typically machined into the piston are one or more ring grooves for supporting piston rings and a combustion bowl. A machinist typically uses a bottom surface of the skirt as a datum, or reference, plane when machining these features into the piston. The combustion bowl may be given a traditional “Mexican Hat” configuration that is typically associated with diesel engine type pistons. The traditional shape is readily formed by turning wherein a cutting tool machines away material from the initial surface of the bowl bowl in one or multiple operations to achieve the final finish.